Full wave envelope detector using current mirrors

Abstract

The fullwave bridge envelope detector comprises first, second, third, and fourth rectifier circuits each of which are coupled to receive first or second alternating input signals which are 180 degrees out of phase. The first and third rectifier circuits each include a diode connected transistor and an additional transistor coupled in current mirror relationship therewith so as to produce halfwave rectified versions of the first and second alternating input signals respectively. The second and fourth rectifier circuits each comprise a transistor which is rendered conductive when first and second alternating input signals respectively become negative. The halfwave rectified signals produced by the first and second rectifier circuits and the halfwave rectified signals produced by the third and fourth rectifier circuits are summed at an output node to produce the fullwave rectified version.

I claim: 
     
       1. A full wave bridge envelope detector, comprising: first rectifier means receiving a first altenrating input signal for producing a first half-wave rectified version of said first alternating input signal, said first rectifier means including first diode means having an anode for receiving said first alternating input signal and having a cathode for coupling to a first source of supply voltage, and a first transistor having an emitter for coupling to said first source of supply voltage, a collector coupled to an output node and a base coupled to the anode of said first diode means;   second recitifer means receiving a second alternating input signal, 180 degrees out of phase with said first alternating input signal, for producing a second half-wave rectified version of said first alternating input signal;   third rectifier means receiving said second alternating input signal and coupled to said second rectifier means for producing a first half-wave rectified version of said second alternating input signal;   fourth rectifier means coupled to said first rectifier means and receiving said first alternating input signal for producing a second half-wave rectified version of said second alternating input signal; and     means for summing said first and second half-wave rectified versions of said first alternating input signal and said first and second half-wave rectified versions of said second alternating input signal to produce a fullwave rectified version indicative of said envelope at said output node.   
     
     
       2. An envelope detector according to claim 1 wherein said second rectifier means comprises a second transistor having a base coupled to a source of a bias voltage, a collector coupled to said output node, and an emitter for coupling to said second alternating input signal. 
     
     
       3. An envelope detector according to claim 2 wherein said third rectifier means comprises: second diode means having an anode for receiving said second alternating input signal and having a cathode for coupling to said source of supply voltage; and   a third transistor having an emitter for coupling to said source of supply voltage, a base coupled to said anode and a collector coupled to said output node.   
     
     
       4. An envelope detector according to claim 3 wherein said fourth rectifying means comprises: a fourth transistor having a base coupled to said source of a bias voltage, a collector coupled to said output node and an emitter coupled to receive said first alternating input signal.   
     
     
       5. An envelope detector according to claim 4 wherein each of said first and second diode means comprises a diode connected transistor.